In situations immediately following a catastrophic event, first responders often must enter a hazardous environment, such as a burning, flooded, or collapsed structure, a cave-in, landslide, or avalanche. While it may not be possible for these persons to be visually observed, it is necessary for safety and efficacy to follow both progress and location of this type of personnel. This is especially true of larger scale operations involving special equipment and more than a few personnel.
If the degree of obstruction is relatively small, then conventional communications devices such as WiFi and cell phones may at least provide a link, if not a location or status. Often, mobile emergency equipment becomes available to provide improved communication capability or even an emergency command center. However, most wireless communication systems used in emergencies operate at higher frequencies and are severely attenuated by obstructions composed of ordinary materials like steel, concrete, rock, soil and water. For example, existing tracking systems based on global positioning satellites (GPS) or ultra-wideband and VHF/UHF time difference of arrival (TDOA) technology are severely attenuated by these types of obstructions, and have therefore proven unsuitable for this purpose.